1. Field of the Invention
The present invention relates to a light emitting diode (LED) module and method of packaging the same, and more particularly, to a high power LED module and method for packaging the same.
2. Description of the Prior Art
In recent years, a new application field of high illumination light emitting diodes (LEDs) has been developed. Different from a common incandescent light, a cold illumination LED has the advantages of low power consumption, long device lifetime, no idling time, and quick response speed. In addition, since the LED also has the advantages of small size, vibration resistance, suitability for mass production, and ease of fabrication as a tiny device or an array device, it has been widely applied in display apparatus and indicating lamps used in information, communication, and consumer electronic products. The LEDs are not only utilized in outdoor traffic signal lamps or various outdoor displays, but are also very important components in the automotive industry. Furthermore, the LEDs work well in portable products, such as cellular phones and as backlights of personal data assistants. These LEDs have become necessary key components in the highly popular liquid crystal displays because they are the best choice when selecting the light source of the backlight module.
Please refer to FIG. 1. FIG. 1 is a cross section diagram showing a conventional LED module. As shown in FIG. 1, the conventional LED module includes a substrate 10, a plurality of LED units 12 positioned above the substrate 10, and a capsulation material layer 14 disposed on the LED unit 12, in which each LED unit 12 includes an LED chip 16, an electrical conductive layer 18 positioned below the LED chip 16, and at least one wire 20 used for connecting the LED chip 16 to the electrical conductive layer 18.
In real applications, the substrate 10 can be a lead frame or a printed circuit board, and the LED chip 16 is fixed onto a positive electrode terminal of the electrical conductive layer 18 via a fixing gel. The positive and negative electrodes on the LED chip 16 are then connected separately to the positive electrode terminal and the negative electrode terminal defined on the electrical conductive layer 18, using a wire bonding technique. The capsulation material layer 14 is composed of mixtures containing resin, wavelength converting materials, fluorescent powder, and/or light-diffusing materials. Next, the capsulation material layer 14 is packaged onto the substrate 10 by a molding or sealant injection method.
According to the conventional method, the package process of the LED unit 12 is performed after the wire bonding and the LED unit 12 is fixed onto the substrate 10. Essentially, a defective LED chip or a poor wire bonding process will result in a nonfunctional LED module, which will also affect the overall reliability and cost of the final product. In order to protect the LED chip and wire, the capsulation material layer 14 is composed primarily of robust and enduring materials. Hence, as the capsulation material layer 14 gets more rigid, the stress level of the overall package structure will increase accordingly, which will easily cause the capsulation material layer 14 to break in half or detach from the substrate 10 and decrease the reliability of the product.
Please refer to FIG. 2. FIG. 2 is a cross-sectional diagram showing a conventional LED module containing a single LED package. As shown in FIG. 2, the LED module includes a substrate 30, an insulating layer 32, a printed circuit board 34 positioned above the substrate 30, and a plurality of LED package bodies 36 disposed on the printed circuit board 34 and electrically connected to the printed circuit board 34. Each LED package body 36 includes an LED chip 40 positioned on the electrical conductive layer 38a, which is used as a positive electrode terminal. The positive electrode and the negative electrode of the LED chip 40 are separately connected to the corresponding positive electrode terminal defined on the electrical conductive layer 38a via a wire 42a and the corresponding negative electrode terminal defined on the electrical conductive layer 38b via a wire 42b. The LED package body 36 also includes a capsulation material layer 44 disposed on the devices including the LED chip 40, the wires 42a and 42b, and the electrical conductive layers 38a and 38b. 
After the construction of the LED package body 36 is completed by forming the capsulation material layer 44 via molding or sealant injection, the entire LED module is then formed by aggregating each of the components including the LED package body 36 on the substrate 30. In a high power LED module, the electrical conductive layer 38a that carries the LED chip 40 has to be designed with a larger volume and has to be made of heat radiating materials to prevent the LED chip 40 from overheating, which may eventually result in a reduction of light intensity or failure of the entire device. In addition to the fact that the volume of the single LED package body 36 is significantly larger than the conventional multiple LED linking package structure, the heat radiating demand required by most high power LED modules adds an extra burden and limitation to the design of the LED module.
In addition, several single LED package structures and methods applicable to high power LED modules have also been disclosed in Taiwan Patent No. 578280 and No. 582122. Taiwan Patent No. 549603, on the other hand, discloses a multiple LED linking package structure. Despite the fact that the LED module formed by the single LED package method is able to effectively reduce the risk of the LED module suffering from conditions such as defective single LED chip or poor wire bonding, numerous uncertainties including higher cost, and unstable heat radiating ability and structure strength still remain unsolved, preventing the single LED chip from being popularized in other product applications.